Sept 18 (Reuters) - Zoox Inc on Friday received a permit from California state authorities to test its self-driving vehicles without an in-car backup driver, marking a win for Amazon.com Inc, which acquired the startup in June.

The world's largest online retailer has been aggressively expanding into self-driving technology, with the company also participating in self-driving car startup Aurora Innovation Inc's $530 million funding round early last year.

The new permit allows Zoox to test two autonomous vehicles without a driver behind the wheel on specified streets near its Foster City headquarters, the state's Department of Motor Vehicles said in a statement.

Other companies who already hold a permit include Alphabet Inc's Waymo, Chinese startup AutoX and Nuro Inc. (Reporting by Akanksha Rana in Bengaluru; Editing by Arun Koyyur, Aditya Soni)